Control device having buttons with automatically adjustable backlighting

ABSTRACT

A control device may comprise a plurality of buttons, a plurality of light sources located behind the respective buttons and configured to illuminate the buttons, a light detector circuit configured to measure an ambient light level around the control device, and/or a control circuit configured to control the light sources to adjust surface illumination intensities of the respective buttons in response to the measured ambient light level. Each button may comprise indicia indicating a function of the button. The control circuit set the first button as active and the second button as inactive in response to an actuation of the first button. The control circuit may, based on the measured ambient light level, control the light sources to illuminate the first button to an active surface illumination intensity, and to illuminate the second button to an inactive surface illumination intensity that is less than the active surface illumination intensity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional U.S. PatentApplication No. 62/166,208, filed May 26, 2015, the disclosure of whichis incorporated herein by reference in its entirety.

BACKGROUND

Home automation systems, which have become increasing popular, may beused by homeowners to integrate and control multiple electrical and/orelectronic devices in their house. For example, a homeowner may connectappliances, lights, blinds, thermostats, cable or satellite boxes,security systems, telecommunication systems, and the like to each othervia a wireless network. The homeowner may control these devices using acontroller, a remote control device (e.g., such as a wall-mountedkeypad), and/or a user interface provided via a phone, a tablet, acomputer, or the like directly connected to the network or remotelyconnected via the Internet. These devices may communicate with eachother and the controller to, for example, improve their efficiency,their convenience, and/or their usability.

The user interface used to control the multiple electrical and/orelectronic devices may provide backlighting that indicates which buttonis selected and which button(s) are unselected. However, the intensityof this backlighting may be inconsistent when viewed in various lightlevels. For example, the user may be able to easily distinguish betweenthe selected and unselected buttons in higher light level situations,but it may be difficult to distinguish between the selected andunselected buttons in low light level situations, or vice versa. Assuch, a need exists to for systems and methods that provide forautomatically adjustable backlighting that, for example, is based on thecurrent ambient lighting conditions in the space.

SUMMARY

The present disclosure relates to a load control system for controllingthe amount of power delivered to an electrical load, such as a lightingload, and more particularly, to a keypad having buttons withbacklighting for use in a load control system.

As described herein, a control device may comprise first and secondbuttons, first and second light sources, a light detector circuit,and/or a control circuit. The first and second light sources may belocated behind the respective buttons and may be configured toilluminate the buttons. The light detector circuit may be configured tomeasure an ambient light level in the vicinity around the controldevice. The control circuit may be configured to control the lightsources to adjust surface illumination intensities of the respectivebuttons in response to the measured ambient light level. One or more ofthe buttons (e.g., each button) may comprise indicia indicating afunction of the button. The control circuit may be responsive toactuations of the buttons. For example, the control circuit may beconfigured to set the first button as active and the second button asinactive in response to an actuation of the first button. The controlcircuit may be configured to control the first and second light sourcesto illuminate the first button to an active surface illuminationintensity and to illuminate the second button to an inactive surfaceillumination intensity that is less than the active surface illuminationintensity. The control circuit may be configured to adjust the activeand inactive surface illumination intensities in response to the ambientlight level measured by the light detector circuit.

The control circuit may be further configured to adjust the active andinactive surface illumination intensities in response to the ambientlight level measured by the light detector circuit using active andinactive adjustment curves stored in memory. The active and inactiveadjustment curves may be non-linearly related. Further, the controlcircuit may provide active or inactive adjustment curves, and forexample, the control circuit may be configured to select a particularactive or inactive adjustment curve based on user selection.

The control device described herein may further comprise a communicationcircuit. The communication circuit may be configured to receive a signalfrom an external device, and the signal may comprise informationrelating to the first and/or second adjustment curves. The informationreceived via the signal may be used by the control circuit to adjust thefirst and/or second adjustment curves. For example, the control circuitmay adjust the first adjustment curve while maintaining the secondadjustment curve the same in response to the information received viathe signal. The control circuit may control a contrast between the firstand second surface illumination intensities associated with the firstand second adjustment curves via the adjustment. The informationreceived via the signal may comprise a scaling factor and/or an offset.The control circuit may be configured to generate the first and secondadjustment curves based on the scaling factor and/or the offset.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a perspective view of an example control device(e.g., a wall-mounted keypad) for use in a load control system forcontrolling the amount of power delivered to one or more electricalloads.

FIG. 2 is a diagram of a block diagram of an example control device.

FIG. 3 is a graph that illustrates example adjustment curves foradjusting duty cycles of currents conducted through light-emittingdiodes illuminating buttons of a control device in response to ameasured ambient light level on a linear scale.

FIG. 4 is a graph that illustrates example adjustment curves foradjusting duty cycles of currents conducted through light-emittingdiodes illuminating buttons of a control device in response to ameasured ambient light level on a logarithmic scale.

FIG. 5 is a flowchart of an example backlighting procedure.

FIG. 6 is a flowchart of another example backlighting procedure.

FIG. 7 is a graph that illustrates example adjustment curves foradjusting duty cycles of currents conducted through light-emittingdiodes illuminating buttons of a control device in response to ameasured ambient light level.

DETAILED DESCRIPTION

FIG. 1 is a diagram of a perspective view of an example control device(e.g., a wall-mounted keypad 100) for use in a load control system forcontrolling the amount of power delivered to one or more electricalloads (e.g., lighting loads). The keypad 100 may comprise a faceplate102 and a plurality of buttons 104 (e.g., four buttons) received throughan opening 106 of the faceplate 102. The faceplate 102 and the buttons104 may comprise a plastic surface, a glass surface, and/or a metallicsurface. The faceplate 102 may be configured to be attached (e.g.,snapped) to an adapter 108, which may be attached (e.g., using screws)to an enclosure (not shown) that houses the electrical circuitry of thekeypad 100.

The keypad 100 may be configured to transmit a digital message to one ormore external load control device via a communication link forcontrolling respective electrical loads. The communication link maycomprise a wired communication link or a wireless communication link,such as a radio-frequency (RF) communication link. Alternatively, thekeypad 100 may comprise an internal load control circuit for controllingthe power delivered to one or more electrical loads. Examples of loadcontrol systems having remote control devices, such as the keypad 100,are described in greater detail in commonly-assigned U.S. Pat. No.6,803,728, issued Oct. 12, 2004, entitled SYSTEM FOR CONTROL OF DEVICES,and U.S. Patent Application Publication No. 2014/0001977, published Jan.2, 2014, entitled LOAD CONTROL SYSTEM HAVING INDEPENDENTLY-CONTROLLEDUNITS RESPONSIVE TO A BROADCAST CONTROLLER, the entire disclosures ofwhich are hereby incorporated by reference.

One or more of the buttons 104 may comprise indicia, such as text 120,for indicating a preset (e.g., a lighting scene) or command (e.g.,on/off, raise/lower, etc.) that may be transmitted in response to anactuation of the button 104. Alternatively or additionally, the indiciaon the button 104 may comprise an icon or symbol. The buttons 104 may bebacklit to allow the indicia to be read in a wide range of ambient lightlevels. Each button 104 may be made of a translucent (e.g., transparent,clear, and/or diffusive) material, such as plastic or glass.Alternatively or additionally, each buttons 104 may comprise a plasticsurface, a glass surface, or a metallic surface. The buttons 104 may beilluminated by one or more light sources (e.g., LEDs) located behind orto the side of each button (e.g., inside of the keypad 100), forexample, such that light is emitted through the indicia and the indiciais illuminated.

In some embodiments, each button 104 may have a translucent body (notshown) and an opaque material, e.g., a metallic sheet (not shown),adhered to a front surface of the body. The text 120 may be etched intothe metallic sheet of each button 104 (e.g., through a machiningprocess, laser cutting, photo-etching, or other metal-removal process).The illumination from the light source may shine through the translucentbody, but not through the metallic sheet, such that the text 120 of eachbutton (e.g., that is etched away from the metallic sheet) isilluminated. Alternatively, the buttons 104 may be coated with anothertype of opaque material, such as paint, and the text 120 may be etchedinto the paint. The body 112 of the button 104 may be made of anothertype of translucent material, such as glass. The opaque material (suchas paint) may be coated onto the rear surface 118 of the body 110 andthe text 118 may be etched into paint on the rear surface of the body.

The faceplate 102 may comprise indicia that, for example, may be backlitto allow the indicia to be read in a wide range of ambient light levels.The indicia of the faceplate 102 may be backlit by one or more lightsources (e.g., LEDs) located behind or to the side of the faceplate 102.For example, the faceplate 102 and the indicia may be composed in amanner similar to the buttons 104 and/or the light source(s) associatedwith the faceplate 102 may be illuminated in a similar manner asdescribed with respect the light sources associated with the buttons104.

One or more of the buttons 104 may be selected by a user (e.g., viaactuation of the button), while the remaining button(s) 104 may beunselected. The keypad 100 may operate to backlight the buttons 104,such that the text 120 of the selected button 104 (e.g., a selectedpreset or an “active” preset) is illuminated to an active surfaceillumination intensity L_(SUR1), and the text 120 of the unselectedbuttons 104 (e.g., the other presets or “inactive” presets) isilluminated to an inactive surface illumination intensity L_(SUR2). Theactive surface illumination intensity L_(SUR1) may be greater than theinactive surface illumination intensity L_(SUR2), such that a user mayidentify which of the buttons 104 is selected based upon the intensityof the illumination of the text 120.

The ambient light level in the room in which the keypad 100 is installedmay affect a user's ability to read the text 120 on the buttons 104.Additionally, the color of the walls, floors, keypad 100, etc. may alsoaffect the surface illumination intensity L_(SUR1), L_(SUR2) perceivedby the user. For example, if the contrast between the brightness of theilluminated text 120 and the brightness of the adjacent surface of thebutton 104 is too low, the illuminated text may appear washed out to theuser. Accordingly, the keypad 100 may comprise an ambient lightdetection circuit (not shown), which may be located inside of the keypadand may be configured to measure the ambient light level in the room inwhich the keypad 100 is installed. For example, the keypad 100 maycomprise an opening 130 in the adapter 108 through which the ambientlight detection circuit may receive light to make a determination of theambient light level in the room. Alternatively or additionally, thekeypad 100 may comprise an opening in the faceplate 102 and/or one ormore of the buttons 104 for allowing the ambient light detection circuitto receive light. In addition, the ambient light detection circuit maybe configured to receive light through the gaps between the buttons 104and/or through the material of the buttons. The ambient light detectioncircuit may also be positioned behind a semi-transparent or dark windowand may be configured to receive light through the window. The keypad100 may comprise a light pipe for directing light from outside of thekeypad to the ambient light detection circuit.

The keypad 100 may be configured to adjust the active and inactivesurface illumination intensities L_(SUR1), L_(SUR2) in response to themeasured ambient light level. For example, the keypad 100 may beconfigured to increase the active and inactive surface illuminationintensities L_(SUR1), L_(SUR2) if the ambient light level increases, andconfigured to decrease the active and inactive surface illuminationintensities L_(SUR1), L_(SUR2) if the ambient light level decreases. Assuch, the keypad 100 may reduce the affect that the ambient light levelin the room and other external factors (e.g., color of the walls, floor,keypad 100, etc.) have on the user's ability to read the text 120 on thebuttons 104, and for example, distinguish between a selected anunselected button 104.

FIG. 2 is a block diagram of an example load control device 200. Thecontrol device 200 may, for example, be deployed as the keypad 100 shownin FIG. 1. The control device 200 may comprise a control circuit 210,which may include one or more of a processor (e.g., a microprocessor), amicrocontroller, a programmable logic device (PLD), a field programmablegate array (FPGA), an application specific integrated circuit (ASIC), orany suitable processing device. The control device 200 may comprise oneor more actuators 212 (e.g., mechanical tactile switches), which may beactuated in response to actuations of the buttons 104. The controlcircuit 210 may be coupled to the actuators 212 for receiving userinputs. Alternatively, the control device 200 may comprise one or moretouchscreen user interfaces instead of physical buttons (e.g., acapacitive based touchscreen, resistive based touchscreen, etc.), andthe control circuit 210 may be coupled to the touchscreen for receivinguser inputs.

The control device 200 may further comprise a communication circuit 214,such as, a wired communication circuit or a wireless communicationcircuit (e.g., an RF transmitter coupled to an antenna for transmittingRF signals). The control circuit 210 may be coupled to the communicationcircuit 214 for transmitting digital messages in response actuations ofthe actuators. Alternatively or additionally, the communication circuit214 may include an RF receiver for receiving RF signals, an RFtransceiver for transmitting and receiving RF signals, or an infrared(IR) transmitter for transmitter IR signals. The control circuit 210 maybe configured to receive a digital message including, for example, aselected preset and/or the status of an electrical load controlled by anexternal load control device. The control circuit 210 may also beconfigured to one or more digital messages including configurationinformation for the control device 200, for example, from a systemcontroller of the load control system in which the control device isoperating and/or from a network device, such as a laptop, a smart phone,a tablet, or similar device.

The control device 200 may also include a memory 216 communicativelycoupled to the control circuit 210. The control circuit 210 may beconfigured to use the memory 216 for the storage and/or retrieval of,for example, commands and/or preset information to transmit in responseto actuations of the buttons 104. The memory 216 may be implemented asan external integrated circuit (IC) or as an internal circuit of thecontrol circuit 210.

The control device 200 may also comprise a power supply 218 forgenerating a direct-current (DC) supply voltage V_(CC) for powering thecontrol circuit 210, the communication circuit 214, the memory 216,and/or other low-voltage circuitry of the control device. The powersupply 218 may be coupled to an alternating-current (AC) power source oran external DC power source via electrical connections 219. The controldevice 200 may comprise an internal power source (e.g., one or morebatteries) for supplying power to the power supply 218.

The control device 200 may comprise a backlighting circuit 220 forilluminating indicia on one or more buttons (e.g., the buttons 104 ofthe keypad 100). For example, the backlighting circuit 220 may comprisefour LEDs 222 coupled respective ports on the control circuit 210respective resistors 224. The control circuit 210 may be configured toindividually turn each LED 222 on by pulling the respective port lowtowards circuit common, such that the LED is coupled between the supplyvoltage V_(CC) and circuit common through the respective resistor 224.The control circuit 210 may be configured to adjust (e.g., dim) theillumination of each LED 222. For example, the control circuit 210 maybe configured to adjust the illumination of an LED 222 by pulse-widthmodulating (PWM) the LED current conducted through the LED and adjustinga duty cycle DC_(LED) of the pulse-width modulated LED current.

While the control device 200 shown in FIG. 2 has one LED 222 forilluminating each of the buttons 104, each LED illustrated in FIG. 2 maycomprise one or more LEDs coupled in series or parallel. For example,each LED 222 in FIG. 2 may comprise four LEDs coupled in series. Forexample, the LEDs 222 may comprise white LEDs. Each of the resistors 224coupled in series with the respective LEDs 222 may have a resistancesized such that the maximum average magnitude of LED current may beapproximately 20 mA.

The control circuit 210 may be configured to backlight buttons (e.g.,the buttons 104), such that the text of a specific button (e.g., abutton having indicia indicating a selected preset, which may bereferred to as “the selected button” or “the active button”) isilluminated to an active surface illumination intensity L_(SUR1), andthe indicia of each of the other buttons (e.g., which may be referred toas “the unselected buttons” or “the inactive buttons”) is illuminated toan inactive surface illumination intensity L_(SUR2), where the inactivesurface illumination intensity L_(SUR2) is less than the active surfaceillumination intensity L_(SUR1). To illuminate the text of one of thebuttons 104 to the active surface illumination intensity L_(SUR1), thecontrol circuit 210 may pulse-width modulate the LED current through theLED behind the selected button using a first LED duty cycle DC_(LED1) tocause the respective LED to illuminate to a first LED illuminationintensity L_(LED1). To illuminate the text of one of the buttons 104 tothe inactive surface illumination intensity L_(SUR2), the controlcircuit 210 may pulse-width modulate the LED current through the LEDbehind the button using a second LED duty cycle DC_(LED2) to cause therespective LED to illuminate to a second LED illumination intensityL_(LED2). The second LED illumination intensity L_(LED2) may be lessthat the first LED illumination intensity L_(LED1), such that the lightilluminated by the second LED is less than the light illuminated by thefirst LED (e.g., the inactive surface illumination intensity L_(SUR2) isless than the active surface illumination intensity L_(SUR1)).

The control circuit 210 may be configured to backlight two or morelocations of the control device 200 to different surface illuminationintensities (e.g., the active surface illumination intensity L_(SUR1)and the inactive surface illumination intensity L_(SUR2)) based on ameasured ambient light level. For example, the control device 200 mayinclude a faceplate (e.g., faceplate 102), and the faceplate may includeindicia (e.g., that may indicate a name of the control device 200, auser's name, and/or other indicia). The control device 200 may beconfigured to illuminate different indicia of the faceplate to differentsurface illumination intensities, and/or the control device 200 may beconfigured to illuminate indicia of the faceplate to one surfaceillumination intensity and one or more buttons to another surfaceillumination intensity. Further, the control circuit 210 may beconfigured to illuminate different locations of a single button of thecontrol device 200 to different surface illumination intensities.

The control device 200 may comprise an ambient light detector 230 (e.g.,an ambient light detection circuit) for measuring an ambient light levelL_(AMB) in the room in which the control device 200 is installed. Theambient light detector 230 may generate an ambient light detect signal,which may indicate the ambient light level L_(AMB) and may be receivedby the control circuit 210. The ambient light detect signal may be ananalog signal or a digital signal. The control circuit 210 may beconfigured to adjust the first and second LED illumination intensitiesL_(LED1), L_(LED2) in response to the measured ambient light levelL_(AMB), for example, as may be determined from ambient light detectsignal. For example, the control circuit 210 may be configured toincrease the first and second LED illumination intensities L_(LED1),L_(LED2) to increase the active and inactive surface illuminationintensities L_(SUR1), L_(SUR2) if the ambient light level increases. Thecontrol circuit 210 may be configured to decrease the first and secondLED illumination intensities L_(LED1), L_(LED2) to decrease the activeand inactive surface illumination intensities L_(SUR1), L_(SUR2) if theambient light level decreases.

The control circuit 210 may be configured to adjust the first and secondLED illumination intensities L_(LED1), L_(LED2) by adjusting the dutycycle DC_(LED) of the LED current through each of the LED behind therespective buttons. For example, the control circuit 210 may adjust thefirst duty cycle DC_(LED1) of the LED current through the LED behind thebutton having the active preset in response to the measured ambientlight level L_(AMB) according an active LED adjustment curveDC_(ACTIVE), and adjust the second duty cycle DC_(LED2) of the LEDcurrent through each of the LEDs behind the buttons having the inactivepresets in response to the measured ambient light level L_(AMB)according an inactive LED adjustment curve DC_(INACTIVE).

The control circuit 210 may store the active LED adjustment curveDC_(ACTIVE) and the inactive LED adjustment curve DC_(INACTIVE) in thememory 216. The active LED adjustment curve DC_(ACTIVE) and the inactiveLED adjustment curve DC_(INACTIVE) may be stored in tables with a valueof the duty cycle DC_(LED) for each of multiple measured ambient lightlevels L_(AMB). The active LED adjustment curve DC_(ACTIVE) and theinactive LED adjustment curve DC_(INACTIVE) may be defined bypredetermined functions characterized by one or more parameters, suchas, a scaling factor (e.g., a slope) and an offset (e.g., a y-axisintercept). The control circuit 210 may be configured to receive theactive LED adjustment curve DC_(ACTIVE) and/or the inactive LEDadjustment curve DC_(INACTIVE) (e.g., the tables and/or the parameters)via the communication circuit 214. The control circuit 210 may thenstore the active LED adjustment curve DC_(ACTIVE) and the inactive LEDadjustment curve DC_(INACTIVE) (e.g., the tables and/or the parameters)in the memory 216. The control circuit 210 may use the active LEDadjustment curve DC_(ACTIVE) to determine the duty cycle DC_(LED) of theLED current through the LED behind the selected (or active) button. Thecontrol circuit 210 may use the inactive LED adjustment curveDC_(INACTIVE) to determine the duty cycle DC_(LED) of the LED currentthrough each of the LEDs behind the unselected (or inactive) buttons.

The active LED adjustment curve DC_(ACTIVE) and the inactive LEDadjustment curve DC_(INACTIVE) (e.g., the values of the table and/or theparameters) may be adjusted. For example, the active LED adjustmentcurve DC_(ACTIVE) and the inactive LED adjustment curve DC_(INACTIVE)may be adjusted by the system controller and/or the network device ofthe load control system, which may transmit new values for the tableand/or parameters to the control circuit 210 via the communicationcircuit 214. Alternatively or additionally, the control circuit 210 maystore multiple curves for each of the active LED adjustment curveDC_(ACTIVE) and the inactive LED adjustment curve DC_(INACTIVE) in thememory 216, and may recall one of the multiple curves for each of theactive LED adjustment curve DC_(ACTIVE) and the inactive LED adjustmentcurve DC_(INACTIVE) in response to a digital message received via thecommunication circuit 214.

FIGS. 3 and 4 are graphs that illustrate example active and inactiveadjustment curves DC_(ACTIVE), DC_(INACTIVE) for adjusting the dutycycle DC_(LED) of the LED current through each of the LEDs in responseto the measured ambient light level L_(AMB). FIG. 3 is a graph 300 thatillustrates example active adjustment curve DC_(ACTIVE) 301 and anexample inactive adjustment curve DC_(INACTIVE) 302 on a linear scale.FIG. 4 is a graph 400 that illustrates example active adjustment curveDC_(ACTIVE) 401 and an example inactive adjustment curve DC_(INACTIVE)402 on a logarithmic scale. A control circuit (e.g., the control circuit210) may store a first adjustment curve (e.g., the active adjustmentcurve DC_(ACTIVE)) in memory for use when determining a first duty cycleDC_(LED) (e.g., for controlling an LED behind the selected button) and asecond adjustment curve (e.g., the inactive adjustment curveDC_(INACTIVE)) in memory for use when determining a second duty cycleDC_(LED) (e.g., for controlling an LED behind an unselected button).

If, for example, the control circuit is using the active and inactiveadjustment curves DC_(ACTIVE), DC_(INACTIVE) 301, 302 and if themeasured ambient light level L_(AMB) is approximately 500 Lux, then thecontrol circuit will determine to control the first duty cycle DC_(LED1)of the LED current through the LED behind the control button having theactive preset (e.g., the selected button) to approximately 66%, anddetermine to control the second duty cycle DC_(LED2) of the LED currentthrough each of the LEDs behind the control buttons having the inactivepresets (e.g., the unselected buttons) to approximately 17%. Similarly,if the control circuit is using the active and inactive adjustmentcurves DC_(ACTIVE), DC_(INACTIVE) 401, 402 and if the measured ambientlight level L_(AMB) is approximately 10 Lux, then the control circuitwill determine to control the first duty cycle DC_(LED1) of the LEDcurrent through the LED behind the control button having the activepreset (e.g., the selected button) to approximately 3.5%, and determineto control the second duty cycle DC_(LED2) of the LED current througheach of the LEDs behind the control buttons having the inactive presets(e.g., the unselected buttons) to approximately 0.4%.

The human eye has a more difficult time discerning contrast in lowambient light levels than in high ambient light levels. Thus, the firstduty cycle DC_(LED1) of the active adjustment curve DC_(ACTIVE) may be,for example, over ten times greater than the second duty cycle DC_(LED2)of the inactive adjustment curve DC_(INACTIVE) near a minimum ambientlight level L_(AMB-MIN) (e.g., approximately 0 Lux) as shown in FIGS. 3and 4. Near a maximum ambient light level L_(AMB-MAX) (e.g.,approximately 1000 Lux), the first duty cycle DC_(LED1) of the activeadjustment curve DC_(ACTIVE) may be, for example, approximately threetimes greater than the second duty cycle DC_(LED2) of the inactiveadjustment curve DC_(INACTIVE).

The active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE)may be non-linearly related (e.g., not proportional), for example, asshown by the example graph 300 in FIG. 3. The difference between theactive and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) maybe non-linear as the ambient light level ranges from the minimum ambientlight level L_(AMB-MIN) to the maximum ambient light level L_(AMB-MAX).The values of the active and inactive adjustment curves DC_(ACTIVE) andDC_(INACTIVE) may be chosen so that the button having the indicia of theactive preset may be visually distinguished (e.g., visually brighter)from the buttons having the indicia of the inactive presets across arange of typical ambient light levels (e.g., between the minimum ambientlight level L_(AMB-MIN) and the maximum ambient light levelL_(AMB-MAX)). The values of the active and inactive adjustment curvesDC_(ACTIVE) and DC_(INACTIVE) may also be chosen so that the buttonhaving the indicia of the active preset (e.g., the selected button) andthe buttons having the indicia of the inactive presets (e.g., theunselected buttons) may be read across a range of typical ambient lightlevels (e.g., between the minimum ambient light level L_(AMB-MIN) andthe maximum ambient light level L_(AMB-MAX)).

FIG. 5 is a flowchart of an example backlighting procedure 500 that maybe executed periodically by a control circuit (e.g., the control circuit210) for backlighting a plurality of buttons of a control device (e.g.,the buttons 104 of the keypad 100). The control circuit may sample theambient light detect signal at 510 and determine the measured ambientlight level L_(AMB) using the magnitude of the ambient light detectsignal at 512. At 514, the control circuit may set a selected-buttonnumber N_(SEL) to be equal to the presently selected button (e.g., thebutton having text indicating the active or selected preset or scene).For example, the number N_(SEL) may be one for the top button, two forthe second button, three for the third button, and four for the bottombutton of the keypad 100 shown in FIG. 1. In other words, if the Eveningbutton is the selected button, the control circuit will set the numberN_(SEL) to three at 514. During the backlighting procedure 500, thecontrol circuit may step through the LEDs behind each of the buttons anddetermine the correct LED illumination intensity for each of thebuttons. The control circuit may use a variable n for stepping throughthe LEDs during the backlighting procedure 500. At 516, the controlcircuit may initialize the variable n to one.

The control circuit may determine if the variable n is equal to theselected-button number N_(SEL) at 518. If the control circuit determinesthat the variable n is equal to the selected-button number N_(SEL) at518 (e.g., the present button is the selected button), then, at 520, thecontrol circuit may determine the first LED duty cycle DC_(LED1) for thenth LED from the active adjustment curve DC_(ACTIVE) (e.g., according tograph 300 or graph 400) using the measured ambient light level L_(AMB).The control circuit may pulse-width modulate the LED current conductedthrough the nth LED using the first LED duty cycle DC_(LED1) at 522. Ifthe control circuit determines that the variable n is not equal to theselected-button number N_(SEL) at 518, then, at 524, the control circuitmay determine the second LED duty cycle DC_(LED2) for the nth LED fromthe inactive adjustment curve DC_(INACTIVE) (e.g., accordingly to graph300 or graph 400) using the measured ambient light level L_(AMB). Thecontrol circuit may pulse-width modulate the LED current conductedthrough the nth LED using the second LED duty cycle DC_(LED2) at 526.

At 528, the control circuit may determine if the variable n is equal toa maximum number N_(MAX) (e.g., the number of buttons 104 on the keypad100). If the control circuit determines that the variable n is not equalto the maximum number N_(MAX) at 528, then, at 530, the control circuitmay increment the variable n by one, and the backlighting procedure 500may loop around to control the intensity of the next LED (e.g., back to518). If the control circuit determines that the variable n is equal tothe maximum number N_(MAX) at 528, then the backlighting procedure 500may exit.

Illumination from the light source (e.g., LED) behind a button, such asthe selected button, may affect the surface illumination intensity ofthe adjacent buttons (e.g., to not be equal to the second surfaceillumination intensity L_(SUR2)). For example, the illumination from theLED behind the selected button may shine directly on and/or be reflectedor refracted onto the rear surfaces of the bodies of the adjacentbuttons and cause the surface illumination intensity of the adjacentbuttons to increase (and not be equal to the second surface illuminationintensity L_(SUR2)). Accordingly, to cause all of the buttons other thanthe selected button to be illuminated to the second illuminationintensity L_(SUR2), the control circuit may be configured to decreasethe intensities of the LEDs of the buttons next to the selected buttonbelow the second LED illumination intensity L_(LED2), such that theresulting illumination intensity of the indicia on the buttons isapproximately the second surface illumination intensity L_(SUR2).

Since the indicia of the buttons may be located at a position other thanthe middle of the button (e.g., towards the topside of the buttons, suchas is shown by the text 120 on the buttons 104), the light source behinda specific button (e.g., the selected button) may have a greater effecton the surface illumination intensity of a button closest to the indiciaof the specific button (e.g., above the specific button) than on thesurface illumination intensity on a button further from the indicia ofthe specific button (e.g., button below that specific button). Forexample, assuming the indicia is located towards the topside of thebuttons and the buttons are configured in a vertical orientation, theLED behind a selected button may cause a first amount of changeΔ_(LED-BELOW) (e.g., approximately 9%) on the surface illumination ofthe button below the selected button and a second, greater amount ofchange Δ_(LED-ABOVE) (e.g., approximately 15%) on the surfaceillumination of the button above the selected button. The first andsecond amount of change Δ_(LED-BELOW), Δ_(LED-ABOVE) may bepredetermined (e.g., and stored in memory) or may be calculated by thecontrol circuit (e.g., using the ambient light detection circuit).

The control circuit may be configured to adjust for the effect caused bythe location of the indicia on the buttons. Using the example providedabove, the control circuit may be configured to control the LED of thebutton below the selected button to a third LED illumination intensityL_(LED3), and to control the LED of the button above the selected buttonto a fourth LED illumination intensity L_(LED4). The fourth LEDillumination intensity L_(LED4) may be less than the third LEDillumination intensity L_(LED3). The control circuit may be configuredto control the illumination of the LEDs to the third and fourth LEDillumination intensities L_(LED3), L_(LED4), for example, by controllingthe LED current through the respective LED using respective third andfourth LED duty cycles DC_(LED2′), DC_(LED2″).

The third and fourth LED duty cycles DC_(LED2′), DC_(LED2″) may becalculated using the inactive duty cycle curve DC_(INACTIVE) and/or thesecond LED duty cycle DC_(LED2). For example, the third and fourth LEDduty cycles DC_(LED2′), DC_(LED2″) may be calculated by multiplying thesecond LED duty cycle DC_(LED2) by predetermine values (e.g., a firstpredetermined value based on the predetermined amount of changeΔ_(LED-BELOW), and a second predetermined value based on thepredetermined amount of change Δ_(LED-ABOVE)). If the indicia on thebuttons is located towards the center of the buttons, the controlcircuit may be configured to control the LEDs of the buttons below andabove the selected button to the same LED illumination intensity (e.g.,the amount of change Δ_(LED-BELOW) may be the same as the amount ofchange Δ_(LED-ABOVE)).

FIG. 6 is a flowchart of another example backlighting procedure 600. Thebacklighting procedure 600 may be executed (e.g., periodically) by acontrol circuit (e.g., the control circuit 210) for backlighting aplurality of buttons of a control device (e.g., the buttons 104 of thekeypad 100). The control circuit may sample an ambient light detectsignal at 610. The control circuit may determine the measured ambientlight level L_(AMB) using the magnitude of the ambient light detectsignal at 612. The control circuit may determine the first LED dutycycle DC_(LED-BELOW) from the active adjustment curve DC_(ACTIVE) (e.g.,accordingly to the graph 300 or the graph 400) using the measuredambient light level L_(AMB) at 614, and may determine the second LEDduty cycle DC_(LED2) from the inactive adjustment curve DC_(ACTIVE)using the measured ambient light level L_(AMB) at 616. At 618, thecontrol circuit may set a selected-button number N_(SEL) to be equal tothe presently selected button (e.g., the selected button having indiciaindicating the active or selected preset or scene). During thebacklighting procedure 600, the control circuit may step through theLEDs behind each of the buttons and determine the correct LEDillumination intensity for each of the buttons. The control circuit mayuse a variable n for stepping through the LEDs during the backlightingprocedure 600. At 620, the control circuit may initialize the variable nto one.

At 622, the control circuit may determine whether the variable n isequal to the selected-button number N_(SEL). If the control circuitdetermines that the variable n is equal to the selected-button numberN_(SEL) at 622 (e.g., the present button is the selected button), thenthe control circuit may control the LED current conducted through theLED behind the selected button using the first LED duty cycle DC_(LED1)at 624. If the control circuit determines that the variable n is notequal to the selected-button number N_(SEL) at 622, then the controlcircuit determines whether variable n is equal to the selected-buttonnumber N_(SEL) plus one at 626. If the control circuit determines thatthe variable n is equal to the selected-button number N_(SEL) plus oneat 626 (e.g., determines that the button is the button below theselected button), then the control circuit may calculate the third LEDduty cycle DC_(LED2′) at 628. For example, the control circuit maycalculate the third LED duty cycle DC_(LED2′) based on the first amountof change Δ_(LED-BELOW) caused by the LED behind the selected button onthe button below the selected button. For example, the control circuitmay calculate the third LED duty cycle DC_(LED2′) according toDC _(LED2′) =DC _(LED2)−(DC _(LED-BELOW) −DC _(LED2))·Δ_(LED-BELOW).At 630, the control circuit may pulse-width modulate the LED currentconducted through the LED behind the button below the selected buttonusing the third LED duty cycle DC_(LED2′).

If the control circuit determines that the variable n is not equal tothe selected-button number N_(SEL) plus one at 626, then the controlcircuit may determine whether the variable n is equal to theselected-button number N_(SEL) minus one at 632. If the control circuitdetermines that the variable n is equal to the selected-button numberN_(SEL) minus one at 632 (e.g., determines that the button is the buttonabove the selected button), then the control circuit may calculate thefourth LED duty cycle DC_(LED2″) at 634. For example, the controlcircuit may calculate the fourth LED duty cycle DC_(LED2″) based on thesecond amount of change Δ_(LED-ABOVE) caused by the LED behind theselected button on the button above the selected button. For example,the control circuit may calculate the fourth LED duty cycle DC_(LED2″)according toDC _(LED2″) =DC _(LED2)−(DC _(LED-BELOW) −DC _(LED2))·Δ_(LED-ABOVE).At 636, the control circuit may pulse-width modulate the LED currentconducted through the LED behind the button above the selected buttonusing the fourth LED duty cycle DC_(LED2″). If the control circuitdetermines that the variable n is not equal to the selected-buttonnumber N_(SEL) minus one at 632, then the control circuit maypulse-width modulate the LED current conducted through the nth LED usingthe second LED duty cycle DC_(LED2) at 638.

After setting the LED illumination intensity at 624, 630, 636, and 638,the control circuit may determine if the variable n is equal to amaximum number N_(MAX) (e.g., the number of buttons 104 on the keypad100) at 640. If the variable n is not equal to the maximum numberN_(MAX) at 640, the control circuit may increment the variable n by oneat 642, before the procedure 600 loops around the set the LEDillumination intensity for the next LED (e.g., the procedure returns to622). If the variable n is equal to the maximum number N_(MAX) at 640,the procedure 600 may exit.

A user may customize one or more of the adjustment curves (e.g., theactive and/or inactive adjustment curves DC_(ACTIVE), DC_(INACTIVE)),for example, using a control device (e.g., the control device 200), anexternal device (e.g., the system controller or the network device ofthe load control system), and/or the ambient light detection circuit.The control device may generate one or more adjustment curves based onuser input. For example, the user may customize one or more adjustmentcurves by adjusting one or more parameters, such as, a scaling factor(e.g., a slope) and/or an offset (e.g., a y-axis intercept) of eachadjustment curve, by adjusting an intensity contrast between the curves,by setting an LED illumination intensity L_(LED) at a particular ambientlight level L_(AMB), and/or the like. When adjusting the parameters ofthe curves, the parameters of both the active adjustment curveDC_(ACTIVE) and the inactive adjustment curve DC_(INACTIVE) may beadjusted (e.g., simultaneously). When adjusting the intensity contrastbetween the curves, the parameters of one of the curves (e.g., theactive adjustment curve DC_(ACTIVE)) may be adjusted while the othercurve (e.g., the inactive adjustment curve DC_(INACTIVE)) remainsconstant. For example, adjusting the parameters of both curves may bebeneficial when the user would like to make both curves more or lessbright, and adjusting the intensity contrast may be beneficial when theuser would like to increase or decrease the contrast between theselected and unselected buttons.

The user may customize an adjustment curve, for example, via a userinterface located on the control device (e.g., the button 104 of thekeypad 100), through an external user interface (e.g., via a smartphonethat communicates with the control device through wirelesscommunication, through a device that communicates with the controldevice through wired communication, etc.), and/or the like. For example,an external device (e.g., smartphone, tablet, PC, etc.) may include auser interface that allows the user to customize one or more adjustmentcurves, and the customized adjustment curve(s) may be downloaded by andstored in memory on the control device. The user may select between aplurality of predefined adjustment curves, and/or the user may createand/or customize one or more adjustment curves. For example, the controldevice may be configured such that the user may set/select the activeand/or inactive surface illumination intensities L_(SUR1), L_(SUR2) forthe when the room is dark (e.g., one or more lights in the room areoff), and set/select the active and inactive surface illuminationintensities L_(SUR1), L_(SUR2) for when the room is bright (e.g., one ormore lights in the room are on, for example, at full intensity).Thereafter, the control device may automatically generate the activeand/or inactive adjustment curves DC_(ACTIVE), DC_(INACTIVE) by scalingbetween those two points. For example, the y-axis intercept of theactive adjustment curve DC_(ACTIVE) may be set according to the selectedactive surface illumination intensity L_(SUR1) at the measured ambientlight level L_(AMB) when the room is dark. The scaling factor of theactive adjustment curve DC_(ACTIVE) may be set so as to cause thepredetermined function defining the active adjustment curve DC_(ACTIVE)to reach the selected active surface illumination intensity L_(SUR1) atthe measured ambient light level L_(AMB) when the room is bright.

A user may customize one or more of the adjustment curves using theambient light detection circuit. The control device may, for example,receive an input (e.g., from an external device) that indicates a changein the ambient light detection circuit, which may adjust one or more ofthe adjustment curves. For example, the input may indicate a change inthe gain of the ambient light detection circuit, which in turn wouldadjust the measured ambient light and the adjustment curves themselves.

After the user creates or selects the adjustment curves, the controlcircuit (e.g., the control circuit 210) may store the customizedadjustment curves (e.g., tables and/or parameters) in memory for usewhen determining a first duty cycle DC_(LED) (e.g., based on the activeadjustment curve DC_(ACTIVE), and for controlling the LED behind theselected button) and a second duty cycle DC_(LED) (e.g., based on theinactive adjustment curve DC_(INACTIVE), and for controlling the LEDbehind an unselected button). The control circuit may be configured with(e.g., store) more than one active adjustment curve DC_(ACTIVE) and/ormore than one inactive adjustment curve DC_(INACTIVE). As such, thecontrol device user may select between multiple active/inactiveadjustment curves quickly and easily. Further, the adjustment curves maybe shared between multiple different control devices (e.g., controldevices located throughout the same room, in different rooms in the samebuilding, and/or in different rooms in different buildings) via directcommunication between the control devices and/or through a central hub.The adjustment curves may be copied from one control device to anothercontrol device (e.g., may be transmitted between control devices andstored by the receiving control device).

FIG. 7 is a graph that illustrates example adjustment curves foradjusting duty cycles of currents conducted through light-emittingdiodes illuminating buttons of a control device (e.g., the controldevice 200) in response to a measured ambient light level. Graph 700illustrates examples of three different active adjustment curves 702,703, and 704, and one example inactive adjustment curve 701. The activeadjustment curve 702 may be considered a low active adjustment curve(e.g., characterized by lower contrast between the intensitiesassociated with the active adjustment curve 702 and the inactiveadjustment curve 701), the active adjustment curve 703 may be considereda medium active adjustment curve (e.g., characterized by a medium amountof contrast between the intensities associated with the activeadjustment curve 703 and the inactive adjustment curve 701), and theactive adjustment curve 704 may be considered a high active adjustmentcurve (e.g., characterized by higher contrast between the intensitiesassociated with the active adjustment curve 704 and the inactiveadjustment curve 701). The medium active adjustment curve 703 may bedetermined based on a first offset value above the low active adjustmentcurve 702, and the high active adjustment curve 704 may be determinedbased on a second offset value above the low active adjustment curve702. The first and second offset values may be functions of the measuredambient light level (e.g., the first and second offset values mayincrease as the measured ambient light level increases).

The control device may receive one of the active adjustment curves 702,703, and 704 via a communication circuit and may store the received oneof the active adjustment curves 702, 703, and 704 in memory for use whendetermining a first duty cycle DC_(LED) (e.g., for controlling the LEDbehind the selected button)

The control devices described herein (e.g., the keypad 100 and/or thecontrol device 200) may be configured to control a variety of electricalloads. For example, one or more of the embodiments described herein maybe performed by a variety of load control devices that are configured tocontrol of a variety of electrical load types, such as, for example, aLED driver for driving an LED light source (e.g., an LED light engine);a screw-in luminaire including a dimmer circuit and an incandescent orhalogen lamp; a screw-in luminaire including a ballast and a compactfluorescent lamp; a screw-in luminaire including an LED driver and anLED light source; a dimming circuit for controlling the intensity of anincandescent lamp, a halogen lamp, an electronic low-voltage lightingload, a magnetic low-voltage lighting load, or another type of lightingload; an electronic switch, controllable circuit breaker, or otherswitching device for turning electrical loads or appliances on and off;a plug-in load control device, controllable electrical receptacle, orcontrollable power strip for controlling one or more plug-in electricalloads (e.g., coffee pots, space heaters, other home appliances, and thelike); a motor control unit for controlling a motor load (e.g., aceiling fan or an exhaust fan); a drive unit for controlling a motorizedwindow treatment or a projection screen; motorized interior or exteriorshutters; a thermostat for a heating and/or cooling system; atemperature control device for controlling a heating, ventilation, andair conditioning (HVAC) system; an air conditioner; a compressor; anelectric baseboard heater controller; a controllable damper; a humiditycontrol unit; a dehumidifier; a water heater; a pool pump; arefrigerator; a freezer; a television or computer monitor; a powersupply; an audio system or amplifier; a generator; an electric charger,such as an electric vehicle charger; and an alternative energycontroller (e.g., a solar, wind, or thermal energy controller). A singlecontrol circuit may be coupled to and/or adapted to control multipletypes of electrical loads in a load control system.

What is claimed is:
 1. A control device comprising: a first button and asecond button; a first light source configured to illuminate the firstbutton, and a second light source configured to illuminate the secondbutton; a light detector circuit configured to measure an ambient lightlevel in a vicinity around the control device; a memory for storing afirst adjustment curve and a second adjustment curve; and a controlcircuit configured to: control the first light source to illuminate thefirst button to a first surface illumination intensity and control thesecond light source to illuminate the second button to a second surfaceillumination intensity, the second surface illumination intensity beingless than the first surface illumination intensity; and adjust the firstsurface illumination intensity in response to the ambient light levelmeasured by the light detector circuit using the first adjustment curve,and adjust the second surface illumination intensity in response to theambient light level measured by the light detector circuit using thesecond adjustment curve.
 2. The control device of claim 1, furthercomprising: a communication circuit configured to receive a signal froman external device, the signal comprising information relating to atleast one of the first adjustment curve or the second adjustment curve;wherein the control circuit is configured to adjust at least one of thefirst adjustment curve or the second adjustment curve stored in thememory in response to the information received via the signal.
 3. Thecontrol device of claim 2, wherein the control circuit is configured toadjust the first adjustment curve and maintain the second adjustmentcurve the same in response to the information received via the signal tocontrol a contrast between the first and second surface illuminationintensities associated with the first and second adjustment curves. 4.The control device of claim 2, wherein the information relating to theat least one of the first adjustment curve or the second adjustmentcurve comprises at least one of a scaling factor or an offset; andwherein the control circuit is configured to generate the first andsecond adjustment curves based on the at least one of the scaling factoror the offset.
 5. The control device of claim 1, wherein the first andsecond light sources comprise respective first and second light-emittingdiodes (LEDs), and the control circuit is configured to pulse-widthmodulate first LED current conducted through the first LEDs to adjustthe first surface illumination intensity, and to pulse-width modulatesecond LED current conducted through the second LEDs to adjust thesecond surface illumination intensity.
 6. The control device of claim 5,wherein the control circuit is configured to determine a first LED dutycycle for the first LED current based on the first adjustment curve, andto determine a second LED duty cycle for the second LED current based onthe second adjustment curve.
 7. The control device of claim 1, whereinthe first and second adjustment curves are non-linearly related.
 8. Thecontrol device of claim 1, wherein the control circuit is configured totransmit a digital message to an external load control device via acommunication link for controlling an external electrical load.
 9. Thecontrol device of claim 8, wherein the communication link comprises awired communication link or a wireless communication link.
 10. Thecontrol device of claim 1, wherein the control circuit is furtherconfigured to set the first button as active and the second button asinactive in response to an actuation of the first button.
 11. Thecontrol device of claim 1, further comprising a communication circuitconfigured to receive a signal from an external device; wherein thecontrol circuit is configured to set the first button as active and thesecond button as inactive based on the signal.
 12. The control device ofclaim 1, wherein the first light source is located behind the firstbutton and the second light source is located behind the second button,or the first light source is located to the side of the first button andthe second light source is located to the side of the second button. 13.The control device of claim 1, wherein the first button comprises firstindicia indicating a function of the first button, and the second buttoncomprises second indicia indicating a function of the second button. 14.The control device of claim 1, further comprising an internal loadcontrol circuit for controlling power delivered to an externalelectrical load.
 15. A control device comprising: a plurality ofbuttons; a plurality of light sources comprising light-emitting diodes(LEDs), wherein each of the plurality of light sources is configured toilluminate a respective button of the plurality of buttons; a lightdetector circuit configured to measure an ambient light level in avicinity around the control device; a memory for storing a firstadjustment curve and a second adjustment curve; and a control circuitconfigured to: set one of the plurality of buttons as active; controlthe light source associated with the active button to illuminate theactive button to an active surface illumination intensity based on ameasured ambient light level measured by the light detector using thefirst adjustment curve; control the light sources associated with theremaining of the plurality of buttons to illuminate the respectivebuttons to an inactive surface illumination intensity using the secondadjustment curve, based on the measured ambient light level, and basedon the relative location of the button with respect to the activebutton, the inactive surface illumination intensity less than the activesurface illumination intensity.
 16. The control device of claim 15,wherein each button comprises indicia that is offset from a center ofthe button, and the control circuit is configured to control the lightsources associated with the remaining of the plurality of buttons toilluminate the respective buttons to the inactive surface illuminationintensity based on the measured ambient light level and based on therelative location of the button with respect to the indicia of theactive button.
 17. The control device of claim 15, wherein the controlcircuit is configured to determine that the active button is active inresponse to an actuation of the active button.
 18. The control device ofclaim 15, further comprising a communication circuit configured toreceive a signal from an external device; wherein the control circuit isconfigured to determine that the active button is active based on thesignal.
 19. A control device comprising: a first button, a secondbutton, and a third button, the first button located above the secondbutton, and the third button located below the second button, the firstbutton comprising first indicia located above a midpoint of the firstbutton and indicating a function of the first button, the second buttoncomprising second indicia located above a midpoint of the second buttonindicating a function of the second button, and the third buttoncomprising third indicia located above a midpoint of the third buttonindicating the function of the third button; a first light sourcecomprising first light-emitting diodes (LEDs) and configured toilluminate the first button, a second light source comprising secondLEDs and configured to illuminate the second button, and a third lightsource comprising third LEDs and configured to illuminate the thirdbutton; a memory for storing an active adjustment curve and an inactiveadjustment curve; a light detector circuit configured to measure anambient light level in a vicinity around the control device; and acontrol circuit configured to: set the first button as active, thesecond button as inactive, and the third button as inactive; control thefirst light source to illuminate the first button to the active surfaceillumination intensity, control the second light source to illuminatethe second button to the inactive surface illumination intensity, andcontrol the third light source to illuminate the third button to theinactive surface illumination intensity, the inactive surfaceillumination intensity being less than the active surface illuminationintensity; determine a first LED duty cycle to pulse-width modulate afirst LED current conducted through the first LEDs to adjust the activesurface illumination intensity in response to the ambient light levelmeasured by the light detector circuit using the active adjustmentcurve; determine a second LED duty cycle to pulse-width modulate asecond LED current conducted through the second LEDs to adjust theinactive surface illumination intensity in response to the ambient lightlevel measured by the light detector circuit using the inactiveadjustment curve; determine a third LED duty cycle to pulse-widthmodulate a third LED current conducted through the third LEDs to adjustthe inactive surface illumination intensity in response to the ambientlight level measured by the light detector circuit using the inactiveadjustment curve, wherein the second LED duty cycle is less than thethird LED duty cycle.
 20. A control device comprising: a first lightsource configured to illuminate a first location of the control device,and a second light source configured to illuminate a second location ofthe control device; a light detector circuit configured to measure anambient light level in a vicinity around the control device; a memoryfor storing a first adjustment curve and a second adjustment curve; anda control circuit configured to: control the first light source toilluminate the first location to a first surface illumination intensityand control the second light source to illuminate the second location toa second surface illumination intensity, the second surface illuminationintensity being less than the first surface illumination intensity; andadjust the first surface illumination intensity in response to theambient light level measured by the light detector circuit using thefirst adjustment curve, and adjust the second surface illuminationintensity in response to the ambient light level measured by the lightdetector circuit using the second adjustment curve.
 21. The controldevice of claim 20, further comprising a faceplate comprising firstindicia and second indicia, the first indicia defining the firstlocation and the second indicia defining the second location.
 22. Thecontrol device of claim 20, further comprising: a faceplate comprisingindicia, the indicia defining the first location; and a buttoncomprising the second location.
 23. The control device of claim 20,further comprising a button comprising the first location and the secondlocation.
 24. The control device of claim 23, wherein the buttoncomprises first indicia indicating a function of the first location ofthe button, and second indicia indicating a function of the secondlocation of the button.
 25. The control device of claim 20, wherein thefirst and second light sources comprise respective first and secondlight-emitting diodes (LEDs); wherein the control circuit is configuredto pulse-width modulate first LED current conducted through the firstLEDs to adjust the first surface illumination intensity, and topulse-width modulate second LED current conducted through the secondLEDs to adjust the second surface illumination intensity, and whereinthe control circuit is configured to determine a first LED duty cyclefor the first LED current based on the first adjustment curve, and todetermine a second LED duty cycle for the second LED current based onthe second adjustment curve.
 26. The control device of claim 20, whereinthe first and second adjustment curves are non-linearly related.